1. Field of the Invention
The present invention relates to a device for adjusting the eccentricity of a lens in a frame (holder).
2. Description of the Related Art
Various devices for adjusting the eccentricity of a lens that is held by a lens frame are known in the art. For instance, in one known device, the eccentricity is adjusted by directly pressing the rim of the lens in a radial direction by an adjustment screw. In another known device, the eccentricity is adjusted by providing an adjustment frame between the lens and the lens frame. In another known device, the eccentricity is adjusted by injecting an adhesive between the rim of the lens and the lens frame. However, these known devices have the following problems. In the above-mentioned first device, pressure on the rim of the lens by the adjustment screw may cause the lens to be distorted. In the above-mentioned second device, the cost of production increases since it is necessary to provide an adjustment frame between the lens and the lens frame. In the above-mentioned third device, the cost of production increases since the lens frame needs to be provided with one or more injection groove or hole through which an adhesive is injected; and it is extremely difficult or almost impossible to remove the lens from the lens frame once lens is cemented to the lens frame.
The primary object of the present invention is to provide a device for adjusting the eccentricity of a lens, wherein the eccentricity can be adjusted using the adjusting device with a high degree of precision even though the structure of the device is simple.
To achieve the object mentioned above, according to an aspect of the present invention, a lens eccentricity adjusting device is provided for adjusting an eccentricity of a lens having a circular rim which is held by a lens frame, the adjusting device including a circular opening formed on the lens frame, the lens being fitted into the circular opening; at least three flat countersunk head screws, each being screwed into the lens frame, the flat countersunk head screws being positioned at substantially regular intervals along a circumference of the lens, each of the flat countersunk head screws including a male thread portion that is screwed into the lens frame and a head portion having a tapered surface which tapers down to the male thread portion; and at least one elastic member positioned between each of the flat countersunk head screws and the rim of the lens. The eccentricity is adjusted by deforming the at least one elastic member so as to apply pressure on the rim of the lens via the tapered surface of a corresponding flat countersunk head screw, in accordance with the amount of which the corresponding flat countersunk head screw is screwed into the lens frame, so that the lens is moved in the circular opening in a radial direction.
In an embodiment, the at least one elastic member is a ring member which is fixed to the lens frame via the flat countersunk head screws to hold the lens between the lens frame and the ring member, so that an axial center of the ring member is substantially coincident with the center axis of the circular opening, wherein the ring member is fixed to the lens frame so that an inner peripheral surface of the ring member is in contact with the rim of the lens. Preferably, the lens frame is made of a macroscopically undeformable material.
Preferably, the ring member includes a tapered surface formed around one end of each of the at least three through holes, wherein each flat countersunk head screw is screwed into the lens frame with the tapered surface of each flat countersunk head screw being in intimate contact with a corresponding tapered surface of each through hole therefor.
Preferably, the ring member includes at least three through holes into which the at least three flat countersunk head screws are respectively inserted to be screwed into the lens frame.
In another embodiment, the at least one elastic member includes at least three ring members into which the at least three flat countersunk head screws are respectively inserted to be screwed into the lens frame, so as to hold the lens between the lens frame and the at least three ring members, wherein each of the at least three ring members is fixed to the lens frame so that an outer peripheral surface of the each ring member is in contact with the rim of the lens. Preferably, the lens frame is made of a macroscopically undeformable material.
Preferably, each of the at least three ring members includes a tapered surface formed around one end of a through hole of each of the at least three ring members. Each of the at least three flat countersunk head screws is screwed into the lens frame with the tapered surface of each of the at least three flat countersunk head screws being in intimate contact with corresponding the tapered surface of each of the at least three ring members.
In another embodiment, the at least one elastic member includes at least three deformable portions formed integrally with the lens frame to correspond to the at least three flat countersunk head screws, each of the at least three deformable portions being in contact with the rim of the lens. Preferably, the lens frame is made of an elastic material.
Preferably, the lens frame includes at least three threaded holes into which the at least three flat countersunk head screws are respectively screwed; and a tapered surface formed around an outer end of each of the at least three threaded holes. Each of the at least three flat countersunk head screws is screwed into corresponding one of the three threaded holes with the tapered surface of each flat countersunk head screw being in intimate contact with a corresponding tapered surface of each threaded hole therefor.
Preferably, the at least one elastic member is formed from a type of engineering plastics.
Preferably, an amount of the eccentricity, that is adjusted according to a variation of the amount of which each of the at least one flat countersunk head screw is screwed into the lens frame, is of the order of several micrometers.
The lens frame can hold another lens, the lens eccentricity adjusting device being operated to adjust the eccentricity of the lens with respect to the another lens.
In an embodiment, the three flat countersunk head screws are positioned at substantially 1200 intervals along the circumference of the lens. According to another aspect of the present invention, a method for adjusting an eccentricity of a lens having a circular rim which is held by a lens frame is provided, including fitting the lens into a circular opening formed on the lens frame; screw-engaging at least three flat countersunk head screws into the lens frame at an equi-angular distance outside and around the circular opening; positioning at least one elastic member between each of the at least three flat countersunk head screws and the rim of the lens; and adjusting the position of the lens in the circular opening by adjusting the screwing position of at least one of the at least three flat countersunk head screws which is screwed into the lens frame so that the lens is moved in the circular opening in a radial direction, wherein the at least one elastic member is depressed by the pressure of the three flat countersunk head screws on the rim of the lens.
The present disclosure relates to subject matter contained in Japanese Patent Application No.2000-016787 (filed on Jan. 26, 2000) which is expressly incorporated herein by reference in its entirety.